The present application relates to the field of signaling devices. Although described with particular application to LED rail and traffic signaling applications, it is to be appreciated that the present application is applicable to other types of signaling devices and operations including, but not limited to, transit, pedestrian, automobile, truck, and marine signaling devices. Those skilled in the art will appreciate applicability of the present application to the applications where it is desirable to reduce the effect of external light loading on signaling devices.
Traditionally, traffic lights have used light bulbs in order to produce light. A colored filter was installed in front of each bulb for producing one of the three traffic lights common colors. However, traffic lights using this technology have some drawbacks. One, the bulbs power consumption is high (each being between 100 W and 160 W), increasing the operation costs. Another problem is the short lifetime of the bulb which decreases with environmental conditions such as vibration and temperature.
LED signal modules are rapidly becoming the world standard for replacing conventional incandescent signal lamps. In recent years, their high-energy efficiency and super-long lives have helped colored LEDs make inroads into applications such as traffic signals and exit signs, interior auto lights and outdoor signs. LED traffic signals offer many benefits that can reduce overall operating and maintenance costs. Reportedly, thirty five to forty percent of traffic signals in North America have been converted to LEDs as municipalities seek to reduce maintenance and energy costs. Some LEDs might last as long as five years in traffic signals and result in energy savings of up to as much as ninety percent.
However, there are certain problems associated with the use of LEDs for signal applications. For example, when the sun or another source of an oncoming light strikes the LED signal head, light enters the system and reflects back out providing a false white signal indication or a washed out indication of other colors. As a result, users do not recognize the traffic signals correctly.
Several solutions have been offered to solve this problem, none of which has produced adequate results. Louvers and sun shields do not help with the oncoming light sources. Another solution is to tin the LEDs. This causes false white positives when the oncoming light strikes the signal head. Polarizing filters have proved to be of little help, since the light entering the system does not show significant polarization. The present application contemplates a new and improved method and apparatus that overcomes the above-referenced problems and others.